1. Field of the Invention
The present invention generally relates to wireless communications and, more particularly, to the creation of an empirical map of wireless coverage which quantifies the quality of wireless coverage over an area and resolves variations of coverage quality over the area to within the geographic accuracy of available location systems, such as the Global Positioning Satellite (GPS) system.
2. Background Description
Coverage areas for communications are defined only approximately by wireless carriers. Carriers do provide geographic maps of predicted coverage areas; however, existing maps do not define the precise degree of the coverage area or the locations of gaps within the advertised area. The imprecision of the existing maps is on the order of miles. Gaps in coverage may be caused by natural landscape features such as low lying valleys or by man made obstructions such as tunnels or tall buildings. Wireless communications providers may provide a disclaimer with their coverage map as an implied acknowledgment of such gaps.
In order to maintain communications for mobile applications, it is necessary that the mobile communications device be located in an area of reliable communications. For example, automobiles when stationary must be located in the reliable area. Today, the user must find such an area by chance or make a choice based upon personal experience. To maintain communications in a vehicle in motion is even more difficult. A moving automobile or truck on a highway will pass in and out of areas where communications are reliable as it moves. Currently, there is no way to predict where the transitions from good to bad communications occur.
The Global Positioning System (GPS) uses a set of twenty-four orbiting satellites to allow users to determine their locations. Systems for automotive use have dropped in price to the point where they can be purchased for a few hundred to a few thousand dollars. These systems are either built in to the vehicle (e.g., the Cadillac On-Star system) or are portable in a lap top computer (e.g., the Delorme GPS Tripmate system). Such systems, however, are essentially passive, one way systems; that is, they provide the driver with position information based on GPS data.
It is therefore an object of the present invention to provide an empirical map of wireless coverage which quantifies the quality of wireless coverage over an area.
It is another object of the invention to provide such an empirical map which resolves variations of coverage quality over the area to within the geographic accuracy of available Global Positioning Satellite (GPS) system. Such accuracy is 100 meters or better today for low cost civilian equipment and will be improved to 10 meters or better in the next decade by the launching of a new satellite system. Better precision is inherent in the system today and may be obtained with differential GPS.
According to the invention, there is provided a system for the production of an empirical map of wireless communication coverage through a process of combining information from individual clients to produce the map which is then shared by all of the clients. White spaces, areas not measured, can be discovered and then explored and added to the map database in a self-teaching process.
The invention provides a method to improve wireless communications by using a digital representation of the coverage map to aid in maintaining a reliable communications link. The invention also includes the adaptation of existing wireless coverage maps of wireless communication providers into the digital domain. The existing maps may then be used as the initial map upon which the empirical map it generated to improve wireless communications for mobile clients.
The empirical map may be generated by combining information from a group of mobile wireless users. The group may consist of a fleet of trucks, taxicabs, government service vehicles, or the customers of a wireless service provider. The mobile vehicles must be equipped with a GPS device or be located by other means such as triangulation. While vehicles are moving, the quality of wireless communication, e.g., signal strength or communication continuity are recorded for each vehicle as a function of positions. The data from all of the vehicles is combined to produce the empirical map. The empirical map may be maintained at a central site and replicated for individual vehicles. The map may then be used to direct mobile users to sites of superior communications reliability, warn mobile users when they are out of the service area or are about to leave the service area, or to regulate data communications automatically to stop and restart communications as a mobile vehicle passes through a gap in coverage. For instance, the data to be sent from a car about to enter a tunnel is stored in a buffer until the car leaves the tunnel.